Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then runs?

[squealer]

Hi all,

My 2006 yamaha 50hp has problems. Here's the scenario I am experiencing on a project boat I recently bought.....
1. compression is 120 psi on all three cylinders.
2. went through carbs, cleaned fuel tank & filters, replaced fuel pump and all fuel lines.
3. new water pump, new foot oil
4. did not replace plugs, as they were nearly new.

Motor starts and idles fine on the earmuffs, will rev up fine also. When in water though, motor will die when accelerating at just above idle (1100rpm). After 10 minutes of this, motor will run normally. I can shut motor off and restart adn it will continue to run normally. But if I leave motor off for 10 minutes, it will again die above idle under load, and then after 10 minutes it will run again.

I am pretty sure it is electrical, but I don't know where to start, other than replace plugs. I have never seen plugs do something like this though, so I don't think this is the problem. What all else is there? CDI unit (which I have read is hard to test but rarely fails), rotor, stator, coils...not sure what else could be problem. Is there a way to test any of these components?

Thanks for any help, I am stumped!!!!

 

[99yam40]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Clean the carbs and the prime start enrichment system.
I think this motor has that and not a choke.
And then follow the link and sycn procedure in service manual after reinstalling them to make sure all is adjusted properly


Motor is running too lean to have any power until it warms up are my thoughts.
But never hurts to make sure spark is good and strong and timing is advancing properly while problems is there

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Clean the carbs and the prime start enrichment system.
I think this motor has that and not a choke.
And then follow the link and sycn procedure in service manual after reinstalling them to make sure all is adjusted properly


Motor is running too lean to have any power until it warms up are my thoughts.
But never hurts to make sure spark is good and strong and timing is advancing properly while problems is there

I have a service manual and will double check the linkage, although I believe it is correct. I did clean the carbs and prime enrichment system, I believe that was only on the center carb, right? I dont think it is a lean condition, but its definitely worh looking in to further. To check spark & timing advance, I will need to take it to the water and load it, correct? What is best / easiest way to check spark conditions once there. Just pull plug wires one at a time and see if anything changes?

 

[99yam40]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

a spark tester with adjustable gap can be picked up at many auto parts places and the timing light will show if you are loosing spark to the wire you hook it to.
Just make sure the timing meets spec at idle and WOT when problem is there and when it is not, just to make sure that is not what is causing no power.
spray a fuel mix into the carbs while problem is there to see if that make cylinders pick up

Motor does not need much fuel in neutral to run at RPMs, but needs more under load.
Might try richining the idle screws just a tad still in spec to see if that will help

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

a spark tester with adjustable gap can be picked up at many auto parts places and the timing light will show if you are loosing spark to the wire you hook it to.
Just make sure the timing meets spec at idle and WOT when problem is there and when it is not, just to make sure that is not what is causing no power.
spray a fuel mix into the carbs while problem is there to see if that make cylinders pick up

Motor does not need much fuel in neutral to run at RPMs, but needs more under load.
Might try richining the idle screws just a tad still in spec to see if that will help

Sounds like good advice, I need a new timing light anyhow!! SO, I guess I will make up a spray bottle, take it to the launch, back it in, and try it. If squirting a little fuel in helps it, I guess it is fuel related. It is just odd how it is all of a sudden, it either runs or it doesn't...seems like that is pretty reliable.
Motor definitely has fire on all three when idling at the house, and holding a hand over the intake has effect on all carbs. I do need to confirm that timing is advancing or not advancing both when motor is running right and when it is not.

But say it turns out to be electrical....I am still betting on this as of now....what would be my next step in trouble shooting. I really don't want to get into a parts changing frenzy because I don't have the ability or knowledge of how to troubleshoot electrical stuff.

Thanks!,
Rich

 

[99yam40]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

A Yamaha service manual for your motor will give steps and specs. not sure what manual you have
It will also tell you what equipment you will need to use.

Did you follow the link and sync procedure in manual after reinstalling the carbs?

If it was electrical you would not have the proper voltages into the CDI and out and spark would not be good and strong
even if timing is not in spec at idle or WOT that would not cause it to die
checking ohms and voltage of coils is fairly straight forward, just need the right test equipment

I am still thinking a fuel problem, easy to test everything but the fuel /air ratio .


The prime start feeds all 3 cylinders through internal passages on intake
If not working properly it will run lean at start up when cold
is red lever in the normal position?

Might try spraying some fuel mix into carbs to see if that helps while problem is there or turn red emergency lever to open to see if that helps

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

I will go back to the manual and re-check the link / sync to make sure I didn't miss anything. Will also take another look at the prime start assy. I did flip the lever while on the water when the boat didn't run, and no change. I did not check the solenoid valve on it, but saw the procedure for testing it. Red lever is in normal position.

For the record, maybe I should add some more history to this motor. Its kind of strange, and a bit long, but you may read something into it that I am missing...

I bought the boat a few months ago from a nice old guy that really didn't know anything about boats, and had nothing but bad luck with this one apparently. Its a 98 model Xpress, that he originally bought equipped with a 60hp Yammie. He got taken, as he shortly thereafter learned that the motor had a cracked crank case that had been patched with an epoxy. The repair was going to be so much that he decided to buy a used 2006 50hp from an outboard repair shop, and do away with any problems with the old '98 model. They did the motor swap, but kept the original 703 control. They threw on an old prop that I doubt seriously was pitched correctly. The guy had several issues with the new motor, mostly around carbs. This was easily explained, as the hoses were rotten. He also had the prop spin, and supposedly pitched (but I know where he had this done, so I have my doubts that this was correct). He finally decided to sell it. He told me that he actually had it sold, and that he and the buyer took it to the water for a test run. He said it ran fine for 5 minutes, then just quit and would only idle, so he idled back to the launch (and of course didn't sell the boat). When I found the boat, the poor guy was disgusted and sold it to me "not running" (it would crank up and idle though). He told me that his mechanic was suspecting the CDI unit may be bad, and he wasnt willing to spend the money on it. I asked if I could check a few things, and checked compression, and foot oil, and looked at the general condition of everything. The boat was in rough shape, but the motor problem seemed pretty simple, and I got it for a song.

I got it home and hooked up the ear muffs, and noticed right away that it just puked water out of the telltale, so I got to thinking that perhaps the motor had just gone into "overheat" mode, and allowed him to idle home. I changed the pump, then pulled and cleaned the carbs (you could tell they had recently been gone into), and discovered the typical ethanol hose rubber in them. I replaced the hoses, and thoroughly cleaned the fuel tank (did everything but the fuel pump). I then proceded to re-do the entire boat, so I pulled the motor and gutted her. Worked on it all winter, and have now finished it and hooked everything back up.

I crossed my fingers, but really expected to not have any problems with it. First time to the water, it did exactly what the guy said, it would not run over 1100rpm without dying. My son and I messed with it for a few minutes, then just fished for a while. When returning to the landing and after idling for 10 minutes, I tried the gas again and it took off, but would not plane. HMMMM... When I got home, I thought about the fuel pump (and wished I would have pumped the bulb while I had it in the water), so I pulled it and checked the diaphragms & checks. No punctures, but I didn't like the way the rubber diaphragm felt (kind of brittle feeling), so I ordered a new pump .

Following weekend, I took it back to the water to try again with the new pump. Same thing. Kept trying, then 10 minutes later she tried to plane off. This time, I told my son (we are both big guys) to get up front, and it planed off. I ran it up, it ran fine but would not get above 4500rpm. The speedo said it was doing 35mph, which was the same top speed the guy had told me it would run when it worked for him (it was reading 35mph, but I estimate we were actually going about 28-30, the speedo is definitely not honest. Since that's not far from what I really though the boat would run, I assumed that the prop was severely over pitched. Keep in mind that the guy I bought the boat was pretty small, and the boat had a whale tail on it when he had it which probably helped it plane. I called the guy from the water, and asked him about how it came out of the water for him. He replied that it wasn't quick, but it did plane OK, and we both agreed that this may have been the whale tail. (the boat has 3 big batteries in the back too).

In the 10 minutes I talked to him, we floated down the river. Then when I started the boat again, it was back to not running off idle. After a few minutes, here it goes again! We shut down and fish for an hour, then same thing on way back to launch.

I hope it is fuel related, and really think the prop is over pitched, but I don't think thats the problem that I am experiencing, or the boat would never have run for the guy. I am confident that I rebuilt the carbs correctly, I have done a few. I guess there is a possibility that there was some crap in the fuel pump that contaminated them again right away, but I think that unlikely.

Long story, but I thought I should tell it to help in troubleshooting. You now know everything that I can think of about it. LOL..

Thoughts?

Thanks,
Rich

 

[99yam40]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Does it still have a wale tail on it?

My 16' xpress SV with a C40TLRX has a tail and I tried removing it when I 1st bought the rig second hand.
would plane but it would porpus real bad unless I put someone on the front of the boat no matter how I trimmed it.
Had to reinstall the tail or pick up some transom wedges to be able to get the motor trimmed down farther. I guess it has to do the the angle of the transom is just not right for these Xpress boats. I know some one with a 17' with a 60 on it and they have a tail too.

All that weight with people, batteries, fuel tank, and motor in the back is just too much. needs better weight distribution to balance out the boat.

Go here and find a rig like you have and see what prop they had on it and what it ran like. Performance Bulletins | Yamaha Outboards

Make sure you click on the archived link to find some with a 50

Then check to see what prop you have, should be stamped on it, but will have to pull prop off to see it I am sure.

Good compression, good spark, and proper timing are easy to test and then you are left with fuel/air ratio to get cylinders to fire properly with the power you need. If the motor is under too much of a load it may magnify your problem. You need to get to 5500 at WOT with the prop and load you run

I would make sure timing is advancing as it should, CDI limits RPM during safe mode by retarding timing.
Testing spark is not a big deal with a spark tester to make sure it will jump the proper gap.
But you can test the peak voltage out puts at all RPM and compare to specs in manual if you use the proper test equipment.
DVA adapter with a regular volt meter is cheaper that buying a special meter.

I had a problem with my motor for a year, missing at high RPMs you could feel power come and go with the miss. This is why I know about what to measure and how.
Turns out a previous owner had drilled out the main jets( I guess trying to make it a 50), once I figured out that they were too big by measuring them and comparing to new ones. I replace all 3 and fixed my problem. too much fuel is like too little, will not allow cylinder to fire properly.

Measuring fuel pressure/ vacuum is also a good idea when having problems.

Spark plug wires and caps (These have ohm testing procedures in manual also) along with the plugs are something else that could cause miss firing

Lots of things to look at, good luck
But you can get there

A hand held GPS will help check you MPH

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Thanks for the website link....I knew Mercury had one that worked pretty good, did not know Yamaha actually had performance tests. Didnt see my exact boat (H50) but came pretty close. The Mercury site sized it with a 11" x 12" pitch (stainless), and Yamaha is a 10-3/4 x 13 (aluminum, so a very close match. I am gonna pull my prop again ....but I don't remember seeing a size on it. I know the shop that had this prop has been known to drastically change pitch, whereas most shops will go up or down 2 inches, so I am afraid there may be no telling what this prop originally was or is. I would guess it is pitched at about a 15 or 16" with the rpm it is turning. I have had Yamaha 60 & 90 hp models in that last few years and have loved them. The boat had the whale tail with the original 60, and also with the 50. I took it off, as I wanted to see where I was at without it. Oddly, with 3 big (27 & 29) batteries in the back, and 2 big guys sitting in it, it does not porpoise badly even without the tail. This may be partially due to the over pitched prop though....it may jump all over the place when I get the right prop on it. I do have a GPS, but didn't have it when I tested boat....but I am pretty confident that my top speed was 28-30, been running that river for a long time.

I have some work to do....Want to get this thing good and reliable for my son. And I really want to get done so I can take the BassCat out of the garage, the little boat is taking up all my time these days.!

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

I pulled the prop today, it did have a number after all! Not sure of the manufacturer, but it was an 11"D x 15"P, (said 11 x 15 - G, not sure about the G). Problem is, it has had work done to it, even a little cupping....like someone was trying to DROP rpm. I can't believe the shop set the poor guy up with this prop....Checked several prop calculators, and most seem to lead to the 12"P for my boat. Rule of thumb is 200RPM per inch, so that would get me to 5100, and a smaller dia (10.5") should give me another 100. Do you think I should get an 11" pitch?

 

[99yam40]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

see if you can borrow one to test with would be my thoughts.
I thought Cupping was for adding some extra speed at higher RRPMs, but I have never messed with that so could be way off

You still need to check the motor to see if it is putting out the HP like it should since it is not functioning 100% properly right now
so basing things off you RPM now is not the best thing
Yamaha does make a test prop to use without running it on open water. Might check with local Yamaha dealer

Make sure the stat is in and it functions properly, as cold running motor does not burn fuel well
And check fuel pump as it could be dumping extra fuel on #3 cylinder if there is a pin hole

 

[Capt Ken]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Take that timing light and with the engine on the water hose, check to see if the timing is advancing when you rev the engine. Being the timing is controled inside the CDI and not the timer base, I'm thinking its in the electronics also. But what is odd, usually the engine will continue running without advancing the timing. Just not have any power.

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

Take that timing light and with the engine on the water hose, check to see if the timing is advancing when you rev the engine. Being the timing is controled inside the CDI and not the timer base, I'm thinking its in the electronics also. But what is odd, usually the engine will continue running without advancing the timing. Just not have any power.

So....I think you are saying to just see if it advancing at all, right? I think I need to have it loaded to actually see where it is advancing to. If I do this check, and the timing is not advancing....maybe I can keep it idleing and check it again in 10 minutes to see if it does.. Would that prove that CDI is the problem, or could it still be something else electrically?

99Yam40 has really got me thinking though about the fuel enrichment system. I havent checked it yet so ensure it is working properly, but it makes sense, especially with the prop issue I have found. It is puzzling, because I still go back to the fact that the guy who had the boat before me said that he took the boat out with a potential buyer and it ran fine for 5 minutes, and then just quit and he idled home, and hasn't run right since. That kind of blows the theory of the fuel enrichment system being the problem. Regardless, I will get a timing light and perform the checks.

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

I have tried a couple of things now, although I haven't had the boat back to the water yet. I have ordered a new prop (10-1/2D x 12P), couldn't find a decent used one.
1. Linc & sync has all bee re-verified, and is correct with the manual
2. Fuel enrichment system has bee disassembled and cleaned again, and I tested and confirmed that the thermo-valve is working properly. The diaphragm is not puntured, and the check valves are seated properly. I did notice that the diaphragm had a tiny bit of a "bulge" or "pillow" look, and am a little unsure about that. I definitely found that the hose going from the crank case to the fuel enrichment system had a tiny hole in it right next to the barb on the carb, so I replaced.(I hope this might have had an effect, but it was small so I have my doubts).
3. Timing appears to be set properly (cant verify till I can apply a load), and definitely advances upon revving, both when motor is cold and when it is hot.
4. did not like the way spark plug boots attach to plugs. Disassembled and found that connection between the wire ends and the little springs n(the things that actually go on the plugs) did not look real good (although they did sent fire to plugs). I re-attached them. Also found that the little aluminum caps that go on the end of the plugs were not tight at all on the plugs, actually loose (have not seen this cause a problem before, but I secured them)
5. Did not mention before, but all jets have been confirmed to be correct, and not drilled out (I did this when I first got the boat).

This boat sure runs great on the water hose...idles fine, and revs instantly.

 

[squealer]

Re: Yamaha 50 TLR 2 stroke power problem.....no power off idle e for10 minutes then r

UPDATE - PROBLEM SOLVED!!
Found time yesterday to get the boat back to the water and test, and had desired results.
Evidently the small hole in the hose that connects the fuel enrichment system to the crankcase was causing the mini fuel pump diaphragms to not operate correctly, and the motor was just too lean to run right when cold. The new prop got the boat to plane great and run at desired RPM, so I am just tickled to know that the CDI unit was not the issue. Thanks to all for the help, especially to 99yam40 for getting me to think about the motor running lean until warm.